Harman US

Lanark, IL Weather & Growing Conditions

This Afternoon
75°F
Showers And Thunderstorms Likely
Showers and thunderstorms likely. Mostly cloudy. High near 75, with temperatures falling to around 72 in the afternoon. Southeast wind around 5 mph. Chance of precipitation is 70%.

7-day forecast

WhenTempForecastWindPrecip
This Afternoon 75°F Showers And Thunderstorms Likely 5 mph SE 67%
Tonight 62°F Showers And Thunderstorms 0 to 10 mph E 92%
Sunday 66°F Patchy Fog 15 mph NE 60%
Sunday Night 55°F Chance Rain Showers 15 mph NE 34%
Monday 63°F Chance Rain Showers 15 mph NE 49%
Monday Night 50°F Rain Showers Likely 15 mph NE 56%
Tuesday 61°F Chance Rain Showers 15 mph NE 53%
Tuesday Night 48°F Partly Cloudy 5 to 15 mph NE 13%
Wednesday 64°F Partly Sunny 10 mph NE 5%
Wednesday Night 50°F Mostly Cloudy 5 to 10 mph NE 1%
Thursday 66°F Partly Sunny 5 mph NE 7%
Thursday Night 53°F Mostly Cloudy 0 to 5 mph NE 10%
Friday 69°F Partly Sunny 0 to 5 mph NE 6%
Friday Night 52°F Partly Cloudy 0 to 5 mph NE 6%

Forecast source: National Weather Service (api.weather.gov). Updated through the day.

Growing snapshot for Lanark, IL

Last spring frost
May 2
First fall frost
Oct 7
Growing season
154 days
Hardiness zone
5a

Explore more for Lanark, IL: full frost dates · planting calendar · Illinois frost dates

Climate data from the nearest NOAA station, Mt Carroll, Il (8.8 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 20, 2026.